The primary goals of this project are to study the development of two forms of visual position sensitivity, or hyperacuity, in normal and strabismic infant monkeys. The two forms of hyperacuity to be studied are vernier acuity and stereoacuity. Normal developmental time courses for these visual functions will be compared with that already described for grating acuity. In addition, they will be compared with the time courses found for infant monkeys with experimentally induced strabismus. The proposed experiments are important for several reasons. First, very little is known about the development of spatial position sensitivity yet it is one of the primate visual system's finest known capabilities. Second, strabismic human adults show deficits in visual hyperacuity that are more profound than deficits in resolution acuity, e.g., grating or Snellen acuity. Third, it is thought that the physiological mechanisms underlying hyperacuity and resolution acuity are different. Knowledge of the relative developmental time courses and their relative disruption in strabismus will lend valuable information to the understanding of the underlying processes. An animal model, in this case the monkey, is needed for this work so that the underlying physiological and anatomical processes can be studied in the same species. The monkey was chosen as a model so that the information gained can be extrapolated to the human with relative confidence.